摘要
圆钢管由于空心薄壁的特点,其径向刚度远远小于其轴向刚度。焊接相贯圆钢管节点中,支管主要承受轴向荷载,从而导致主管主要承受径向力作用。此外,节点部位由于曲率不连续而带来很大的应力集中现象。这些原因造成管节点最常见的破坏方式是主管表面靠近焊接部位的局部屈曲或屈服破坏。
为了提高主管的径向刚度,改善节点的受力性能,采用环口板对普通圆钢管进行了加强。环口板加强是一种比较新颖的加强方法,该方法施工方便快捷而且加强效果显著。为了研究环口板加强后管节点的滞回性能,分别对4个足尺度未加强T型圆钢管节点和4个对应的采用环口板加强的足尺度T节点试件进行了轴向反复荷载作用下的拟静力滞回性能研究。基于试验测试结果,发现加强后的管节点在提高静力承载力的同时,其延性指标也有所提高,从而耗能性能更好,利于抗震。根据试验现象发现:采用环口板加强的T节点,可以将破坏发生的部位由原来未加强节点的焊趾处转移到环口板与主管表面焊缝连接处,改变了管节点的破坏模式。
随后提出了环口板加强T节点的有限元模型,采用提出的有限元模型对试验的8个试件进行了模拟分析,结果表明有限元结果和试验测试结果吻合较好,从而验证了有限元模型的准确性。在此基础上,运用所提出的有限模型研究了环口板的几何参数lc(环口板长度)和tc(环口板厚度)对管节点滞回性能的影响,给出了几何参数的取值建议。本文还还分别对lc与tc的加强效果进行了比较,发现后者的加强效果总体上优于前者的加强效果。这些研究对实际工程中管节点的环口板加强设计有重要参考价值。
For a circular tube member, its radial stiffness is generally much smaller than its axial stiffness due to its hollow section and thin wall. In a welded tubular joint, the brace is mainly subjected to axial load, which causes the chord to be subjected to radial load. Furthermore, high stress concentration exists at the joint because the curvature is uncontinuous. Because of the above reasons, the common failure mode for a tubular joint is local buckling or yielding on the chord surface near the weld toe.
In order to increase the stiffness of the chord and to improve the bearing capacity of the tubular joint, collar plate reinforcement is adopted to strengthen the tubular joint. Collar plate reinforcement is a new reinforcing method for tubular joints, and it is of fast fabrication and of markable efficiency. To carry out study on the behaviour of tubular joints after reinforced with collar plate, the hysteretic behaviour of 4 full-scale un-reinforced tubular T-joints and 4 corresponding specimens reinforced with collar plate under quasi-static axial cyclic loading is carried out experimentally. Based on the experimental results, it is found that both the static strength and the ductility are increased for the reinforced specimens, and thus the reinforced T-joints can dissipate more energy caused by seismic action. It is also found from the experimental phenomenon that the failure position is located at the corner of the collar plate, which is much different from the un-reinforced specimen for which the failure position is located at the weld toe along the brace/chord intersection.
Thereafter, the finite element (FE) analysis on the above 8 specimens are conducted. The numerical results agree with the experimental results well, and the presented FE model is proved to be accurate enough for analyzing the hysteretic performance of T-joints with collar plate reinforcement. The effect of the reinforced parameters, namely tc and lc, on the hysteretic performance of the T-joints with collar plate reinforcement are studied based on a parametric study and suggestions for choosing the reinforced parameter values are given. Comparing the enhanced effects of lc and tc, it is found that the second model is more effective than the first model. The results are significant for the design of collar plate reinforcement for tubular joints in practical engineering.
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